(originally posted on Bring Your Own Design)
With today’s WordPress 4.0 sendout, embedding content from other sites just got way easier. While there is a pretty large list of oEmbed providers, a very important one for us SEOs was left out: Wistia. Don’t worry, though. There is a way to make Wistia videos work the same was with a simple paste of the video URL, much like a YouTube video works.
In your theme’s functions.php, paste the following code:
wp_oembed_add_provider( '/https?://(.+)?(wistia.com|wi.st)/.*/', 'https://fast.wistia.com/oembed', true );